An inkjet printer (hereinafter referred to as IJP) is widely used for applications such as printing characters to represent a production lot number, a production date, an expiration date, etc. upon a product. Especially, in the food industry or the like, a production time is often printed together with an expiration date and, lately, a requirement has been made to print a time in hours, minutes, and even seconds.
To fulfill the above requirement, an IJP acquires time information from a Real Timer Clock (hereinafter referred to as RTC) and, using the time information, displays a time on screen and automatically updates and creates print data representing current time information and prints a time (hereinafter referred to as calendar printing). However, when calendar printing is performed with a plurality of IJPs, because the RTC of each IJP operates asynchronously, synchronizing times must be performed manually for calendar printing of a same time with the IJPs, each time a difference between times occurs, and this requires a lot of labor.
As a background art in the present technical field, there is Japanese Unexamined Patent Application Publication No. 2003-182060 (Patent Literature 1). Patent Literature 1 describes an inkjet printing system which includes a plurality of IJPs that print time information on one printing object and which is arranged such that updating time information to be printed by the plurality of IJPs is managed by a common main controlling device to avoid inconsistency of times to be printed by each IJP.